Single-walled carbon nanotubes (SWCNTs) have remarkable electrical and optical properties, particularly when they are individually dispersed. However, high concentrations of individually dispersed nanotubes have been difficult to attain, which has hampered the adoption of solution-based technologies such as self-assembly, thin-film coating, fiber spinning, and printing. In addition to individually dispersed solutions, recent work in thin-film transistor devices has underscored the need for producing bulk quantities of nanotubes that can remain individually dispersed after drying and/or curing.
One of the interesting properties of SWCNTs is the optical absorption and emission features that are associated with the electronic transitions between van Hove singularities (kinks) in the density of states. These optical properties make it possible to take advantage of the unique near-infrared (NIR) fluorescence of SWCNTs as a spectral signature in applications such as document security. Tuning of the band-gap fluorescence by the surrounding environment or through chemical doping methods also enables nanotube applications such as bio-optical sensors. However, these sharp optical absorption features appear only when the nanotubes are well dispersed. Due to coupling of electronic states, fluorescence is often completely quenched when nanotubes are bundled, especially when metallic nanotubes are present. Thus, there is a need for improved nanotube compositions and methods of using them, which is addressed by the present disclosure.